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import re
from collections import ChainMap
from functools import reduce
from mistletoe.base_renderer import BaseRenderer
from mistletoe import span_token, block_token
from mistletoe.core_tokens import MatchObj
class Program(block_token.BlockToken):
def __init__(self, lines):
self.children = span_token.tokenize_inner(''.join([line.strip() for line in lines]))
class Expr(span_token.SpanToken):
@classmethod
def find(cls, string):
matches = []
start = []
for i, c in enumerate(string):
if c == '(':
start.append(i)
elif c == ')':
pos = start.pop()
end_pos = i + 1
content = string[pos + 1:i]
matches.append(MatchObj(pos, end_pos, (pos + 1, i, content)))
return matches
def __repr__(self):
return '<Expr {}>'.format(self.children)
class Number(span_token.SpanToken):
pattern = re.compile(r"(\d+)")
parse_inner = False
def __init__(self, match):
self.number = eval(match.group(0))
def __repr__(self):
return '<Number {}>'.format(self.number)
class Variable(span_token.SpanToken):
pattern = re.compile(r"([^\s()]+)")
parse_inner = False
def __init__(self, match):
self.name = match.group(0)
def __repr__(self):
return '<Variable {!r}>'.format(self.name)
class Whitespace(span_token.SpanToken):
parse_inner = False
def __new__(self, _):
return None
class Procedure:
def __init__(self, expr_token, body, env):
self.params = [child.name for child in expr_token.children]
self.body = body
self.env = env
class Scheme(BaseRenderer):
def __init__(self):
self.render_map = {
"Program": self.render_program,
"Expr": self.render_expr,
"Number": self.render_number,
"Variable": self.render_variable,
}
block_token._token_types = []
span_token._token_types = [Expr, Number, Variable, Whitespace]
self.env = ChainMap({
"define": self.define,
"lambda": lambda expr_token, *body: Procedure(expr_token, body, self.env),
"+": lambda x, y: self.render(x) + self.render(y),
"-": lambda x, y: self.render(x) - self.render(y),
"*": lambda x, y: self.render(x) * self.render(y),
"/": lambda x, y: self.render(x) / self.render(y),
"<": lambda x, y: self.render(x) < self.render(y),
">": lambda x, y: self.render(x) > self.render(y),
"<=": lambda x, y: self.render(x) <= self.render(y),
">=": lambda x, y: self.render(x) >= self.render(y),
"=": lambda x, y: self.render(x) == self.render(y),
"true": True,
"false": False,
"cons": lambda x, y: (self.render(x), self.render(y)),
"car": lambda pair: self.render(pair)[0],
"cdr": lambda pair: self.render(pair)[1],
"and": lambda *args: all(map(self.render, args)),
"or": lambda *args: any(map(self.render, args)),
"not": lambda x: not self.render(x),
"if": lambda cond, true, false: self.render(true) if self.render(cond) else self.render(false),
"cond": self.cond,
"null": None,
"null?": lambda x: self.render(x) is None,
"list": lambda *args: reduce(lambda x, y: (y, x), map(self.render, reversed(args)), None),
"display": lambda *args: print(*map(self.render, args)),
})
def render_program(self, token):
return self.render_inner(token)
def render_inner(self, token):
result = None
for child in token.children:
result = self.render(child)
return result
def render_expr(self, token):
proc, *args = token.children
proc = self.render(proc)
return self.apply(proc, args) if isinstance(proc, Procedure) else proc(*args)
def render_number(self, token):
return token.number
def render_variable(self, token):
return self.env[token.name]
def define(self, *args):
if len(args) == 2:
name_token, val_token = args
self.env[name_token.name] = self.render(val_token)
else:
name_token, expr_token, *body = args
self.env[name_token.name] = Procedure(expr_token, body, self.env)
def cond(self, *exprs):
for expr in exprs:
test, value = expr.children
if test == 'else' and 'else' not in self.env:
return self.render(value)
if self.render(test):
return self.render(value)
def apply(self, proc, args):
old_env = self.env
self.env = proc.env.new_child()
try:
for param, arg in zip(proc.params, args):
self.env[param] = self.render(arg)
result = None
for expr in proc.body:
result = self.render(expr)
finally:
self.env = old_env
return result
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